Backbone.Collection

Collections are ordered sets of models. You can bind “change” events to be notified when any model in the collection has been modified, listen for “add” and “remove” events, fetch the collection from the server, and use a full suite of Underscore.js methods.

Any event that is triggered on a model in a collection will also be triggered on the collection directly, for convenience. This allows you to listen for changes to specific attributes in any model in a collection, for example: documents.on(“change:selected”, …)

extendBackbone.Collection.extend(properties, [classProperties])
To create a Collection class of your own, extend Backbone.Collection, providing instance properties, as well as optional classProperties to be attached directly to the collection’s constructor function.

modelcollection.model([attrs], [options])
Override this property to specify the model class that the collection contains. If defined, you can pass raw attributes objects (and arrays) and options to add, create, and reset, and the attributes will be converted into a model of the proper type using the provided options, if any.

var Library = Backbone.Collection.extend({
  model: Book
});

A collection can also contain polymorphic models by overriding this property with a constructor that returns a model.

var Library = Backbone.Collection.extend({

  model: function(attrs, options) {
    if (condition) {
      return new PublicDocument(attrs, options);
    } else {
      return new PrivateDocument(attrs, options);
    }
  }

});

modelIdcollection.modelId(attrs)
Override this method to return the value the collection will use to identify a model given its attributes. Useful for combining models from multiple tables with different idAttribute values into a single collection.

By default returns the value of the attributes’ idAttribute from the collection’s model class or failing that, id. If your collection uses a model factory and those models have an idAttribute other than id you must override this method.

var Library = Backbone.Collection.extend({
  modelId: function(attrs) {
    return attrs.type + attrs.id;
  }
});

var library = new Library([
  {type: 'dvd', id: 1},
  {type: 'vhs', id: 1}
]);

var dvdId = library.get('dvd1').id;
var vhsId = library.get('vhs1').id;
alert('dvd: ' + dvdId + ', vhs: ' + vhsId);

preinitializenew Backbone.Collection([models], [options])
For use with collections as ES classes. If you define a preinitialize method, it will be invoked when the Collection is first created and before any instantiation logic is run for the Collection.

class Library extends Backbone.Collection {
  preinitialize() {
    this.on("add", function() {
      console.log("Add model event got fired!");
    };
  }
}

constructor / initializenew Backbone.Collection([models], [options])
When creating a Collection, you may choose to pass in the initial array of models. The collection’s comparator may be included as an option. Passing false as the comparator option will prevent sorting. If you define an initialize function, it will be invoked when the collection is created. There are a couple of options that, if provided, are attached to the collection directly: model and comparator.
Pass null for models to create an empty Collection with options.

var tabs = new TabSet([tab1, tab2, tab3]);
var spaces = new Backbone.Collection(null, {
  model: Space
});

modelscollection.models
Raw access to the JavaScript array of models inside of the collection. Usually you’ll want to use get, at, or the Underscore methods to access model objects, but occasionally a direct reference to the array is desired.

toJSONcollection.toJSON([options])
Return an array containing the attributes hash of each model (via toJSON) in the collection. This can be used to serialize and persist the collection as a whole. The name of this method is a bit confusing, because it conforms to JavaScript’s JSON API.

var collection = new Backbone.Collection([
  {name: "Tim", age: 5},
  {name: "Ida", age: 26},
  {name: "Rob", age: 55}
]);

alert(JSON.stringify(collection));

synccollection.sync(method, collection, [options])
Uses Backbone.sync to persist the state of a collection to the server. Can be overridden for custom behavior.